Food-Plants of ‘Monarch’ Butterfly Larvae

Food-Plants of ‘Monarch’ Butterfly Larvae

As many enquiries are made each season, and as early records are somewhat confusing, it is considered as well to clarify the position concerning food-plants of ‘monarch’ butterfly larvae in New Zealand. In various early records the ‘monarch’, Danaus plexippus Linnaeus, 1758. was recorded under the names archippus, erippus, and berenice.

Fereday (1874b BNZE) recorded that a Mr. Meinertzhagen was told by the Maoris that ‘The caterpillar … feeds upon the pollen of the gourd which they grow in that part of the country (Hawke Bay).’ This record is not reliable and is not accepted. Fereday also recorded caterpillars and pupae found by a Mr. Nairn who ‘… had been feeding some new kind of caterpillar …’ and had described ‘… the shrub on which he found the caterpillar as the Gomphocarpus ovata, one of the milk producing plants, and a native of the Cape of Good Hope.’ It is considered by the present author that this is a valid record of Asclepias fruticosa (= Gomphocarpus fruticosus) as a food-plant of Danaus plexippus. A. fruticosa, the common ‘swan plant’, was recorded as a horticultural escape in New Zealand, under the name of Asclepias nivea, by Kirk (1870), and this species is a native of the Cape of Good Hope.

T. B. Gillies (1875 BNZE) quoted a letter (dated December 1, 1874) from Major Von Stürmer in which the latter wrote ‘… the plant that it feeds upon (I call it the scarlet cotton) …’ This record suggests the red flower of Asclepias curassavica but, as it is not known if this plant was at that time present in New Zealand, it seems best to consider the record as Asclepias sp. Colenso (1878 BNZE) was alos obviously referring to an Asclepias when he described ‘cotton plants’ and ‘… green capsule having the remains of soft spines …’. Records by Butler (1878 BNZE) and G. V. Hudson (1898 BNZE. 1928a BNZE) are quoted from an American author and must be disregarded. W. W. Smith (1893a BNZE) stated ‘The food-plant of the larva is now established in several districts in New Zealand’, but unfortunately, he did not name it. A further record of Asclepias sp. was given by P. Marshall (1896d BNZE) who mentioned that ‘In 1894 the usually rare Danais archippus became abundant in Wanganui
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breeding in hundreds on plants of a species of Gomphocarpus, …’. J. J. Walker (1914 BNZE) mentioned Gomphocarpus fruticosus R.Br. as a food-plant at Sydney (Australia) but did not record it as such in New Zealand. Tillyard (1926b BNZE) recorded two plant species, as ‘… Asclepias physocarpa (Gomphocarpus fruticosus) and A. curassiva.’, but as they were not specifically for New Zealand they are here considered to be Australian records. G. V. Hudson (1939 BNZE) recorded ‘… swan plant, Gomphocarpus fruticosus,’, while Cottier (1956) gave the first record of Araujia sericofera as a food-plant in this country.

The known food-plants in New Zealand are all of the family Asclepiadaceae, members of which are sometimes known as ‘milkweeds’ or ‘cotton plants’. The species concerned are as follows :-

Asclepias curassavica L. Commonly known as the ‘blood flower’ this plant has also been called ‘red-head cotton’ in Australia. It is not common in New Zealand but is grown in some gardens and is known to be a food-plant here. This is the first undoubted record for this country.

Asclepias fruticosa L. (= Gomphocarpus fruticosus R. Br.), This, the ‘swan plant’, is generally known as a food-plant in New Zealand. In Australia it has been known as ‘bladder cotton’, ‘white cotton’, etc. Asclepias physocarpa Schlect. (= Gomphocarpus fruticosus Sims, not R. Br.) is a species very close to A. fruticosa L. and. although apparently not known in New Zealand (apart from one mention in a commercial catalogue), may well be grown here under the name of ‘swan plant’. It is a potential food-plant.

Araujia sericofera Brot. (= Araujia sericifera auct.), Although ‘monarch’ caterpillars are not known to occur naturally on the ‘moth-catching plant’ they will readily feed on leaves of this plant when supplies of the ‘swan plant’ have been eaten out.

References

All references included in the ‘Bibliography of New Zealand Entomology’ (Miller, 1956) are referred to that work, in the above text, by the appropriate date and letter, followd by the letters BNZE. e.g. Butler (1878 BNZE), Fereday (1874b BNZE). Other references are given below.